面向构态切换稳定性的约束变胞机构可靠性优化设计方法

Reliability Optimization Design Method of Constrained Metamorphic Mechanism Oriented to the Stability of Configuration Transformation

为获得稳定、可靠的构态切换能力而开展可靠性优化设计是降低约束变胞机构运动功能失效概率的关键。基于多构态欠驱动约束变胞源机构的组成原理建立了含变胞运动副的扩展Assur杆组的模块化受力分析模型。根据变胞运动副的等效阻力梯度模型,考虑系统内外部误差的随机性,利用可靠性理论建立了约束变胞机构构态切换能力的概率评估模型。基于可靠性评估及可靠性灵敏度分析,提出了面向约束变胞机构构态切换稳定性的可靠性优化设计方法,进而针对可靠性灵敏度较高的结构参数随机变量的公差进行优化设计,使优化后的设计方案同时满足可靠性和经济性要求。最后,以折纸变胞机构为例,验证了提出的可靠性优化设计方法的可行性和有效性。研究工作为开展面向高概率的构态切换重复执行能力的变胞机构可靠性优化设计奠定了基础,同时对推进变胞机构的工程应用具有理论和实际意义。

Reliability optimization design to obtain stable and reliable configuration transforming ability is the key to reduce the failure probability of kinematic failure of the constrained metamorphic mechanism.Based on structure composition principle of the multiconfiguration source metamorphic mechanism that can operate in an under-actuated state,the modularized calculation models are established for force analysis of the augmented Assur groups including metamorphic joints.According to the equivalent resistance gradient model of metamorphic joints,with considering the uncertainties in the link dimensions,masses,and compliance parameters et al,a probabilistic evaluation method of the configuration transforming ability of the constrained metamorphic mechanism is established.Based on reliability evaluation and reliability sensitivity analysis,a reliability optimization design method for the configuration transformation of constrained metamorphic mechanisms is proposed,and then the optimization design for tolerances of random variables of structural parameters with high reliability sensitivity is completed,so that the optimized scheme can satisfy both the reliability and economic requirements simultaneously.Finally,the feasibility and effectiveness of the proposed reliability optimization design method is verified by taking the metamorphic mechanism of paper folding as an example.This research provides the foundation of reliability design of metamorphic mechanisms to obtain the high-probability repeated execution ability of configuration transformation,it also has theoretical and practical significance to promote the application of metamorphic mechanisms.